Various types of electronic musical instruments have been available for many years. Perhaps the best known type of electronic instrument is the electronic organ in which a set of tone generators produces electrical oscillation and those oscillations are then passed through filters to filter out the undesired tonal aspects and then to an amplifier which amplifies the tone and provides it to a loudspeaker. The tone generator conventionally is a feedback oscillator connected to a frequency divider, or, alternatively, vibrating metal reeds for generating the tone. The filters are applied to the signal received from the generators to filter out undesired overtones and pass through only the portions of the generated signal which resemble the sound being desired.
Another structure similar to an electronic organ but capable of far more complex tonal output is that commonly referred to as the Moog synthesizer, which similarly functions by applying filters to the output of a signal generator to filter out unwanted components. In both of these types of prior art instruments it has been necessary to provide at least twelve oscillators for the top octave of musical notes to be produced. The lower octaves are then obtained from these oscillators by circuits which divide the frequency to obtain the other, lower octaves. The necessity for this plurality of oscillators or signal generators has meant that there has been substantial complexity and attendant expense in these prior art devices. It has also been found inefficient to obtain a tone corresponding to a predetermined waveform by producing a signal having a substantially more complex waveform and then utilizing filtering to remove the undesired components.